1. Field of the Invention
The present invention relates to a moving picture compression technique, and more particularly, to a loop filtering method in a video coder.
2. Description of the Background Art
Generally, it has been proved that the “H.26L” system developed as a next generation moving picture compression technique is superior to the “H.263” and “MPEG4” systems in performance.
The “H.26L” system as the next generation moving picture compression system differs from the conventional H.263 and MPEG4 in using 4×4 block based transformation & encoding, carrying out motion estimation & compensation of a transformation block size, and using a single variable length coder (VLC).
Superior to the conventional motion picture standards in aspect of performance, the H.26L system has excessive calculation of encoder as well as uses 4×4 block based transformation so that a blocking dominates than the conventional standards.
In order to remove the blocking, filters include a loop filtering system inside the encoder and decoder, a post filter processed in a next stage of the decoder, and a system adding the loop filtering system to the post filter.
When the blocking is removed by the loop filtering system in general, a difference between an input video and a motion video is affected so that an encoding rate increases in a specific case. Yet, as the loop filtering system is installed inside a video coder, complexity of the encoder increases.
As mentioned in the above explanation, the H.26L system according to the related art requires excessive quantity of calculation despite the superiority in performance to the moving picture standards as well as having the blocking more dominant than that of the moving picture standards due to the 4×4 block based transformation system.
Moreover, if the blocking is removed by the loop filtering system according to the related art, the difference between the input video and the motion video is affected so as to increase the encoding rate in a specific case. Yet, the loop filtering system built inside the video coder increases the complexity of the encoder.